SF Patch #1013667: Cleanup Peepholer Output
* Make a pass to eliminate NOPs. Produce code that is more readable,
more compact, and a tiny bit faster. Makes the peepholer more flexible
in the scope of allowable transformations.
* With Guido's okay, bumped up the magic number so that this patch gets
widely exercised before the alpha goes out.
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
new file mode 100644
index 0000000..6c1900d
--- /dev/null
+++ b/Lib/test/test_peepholer.py
@@ -0,0 +1,104 @@
+import dis
+import sys
+from cStringIO import StringIO
+import unittest
+
+def disassemble(func):
+ f = StringIO()
+ tmp = sys.stdout
+ sys.stdout = f
+ dis.dis(func)
+ sys.stdout = tmp
+ result = f.getvalue()
+ f.close()
+ return result
+
+def dis_single(line):
+ return disassemble(compile(line, '', 'single'))
+
+class TestTranforms(unittest.TestCase):
+
+ def test_unot(self):
+ # UNARY_NOT JUMP_IF_FALSE POP_TOP --> JUMP_IF_TRUE POP_TOP'
+ def unot(x):
+ if not x == 2:
+ del x
+ asm = disassemble(unot)
+ for elem in ('UNARY_NOT', 'JUMP_IF_FALSE'):
+ self.assert_(elem not in asm)
+ for elem in ('JUMP_IF_TRUE', 'POP_TOP'):
+ self.assert_(elem in asm)
+
+ def test_elim_inversion_of_is_or_in(self):
+ for line, elem in (
+ ('not a is b', '(is not)',),
+ ('not a in b', '(not in)',),
+ ('not a is not b', '(is)',),
+ ('not a not in b', '(in)',),
+ ):
+ asm = dis_single(line)
+ self.assert_(elem in asm)
+
+ def test_none_as_constant(self):
+ # LOAD_GLOBAL None --> LOAD_CONST None
+ def f(x):
+ None
+ return x
+ asm = disassemble(f)
+ for elem in ('LOAD_GLOBAL',):
+ self.assert_(elem not in asm)
+ for elem in ('LOAD_CONST', '(None)'):
+ self.assert_(elem in asm)
+
+ def test_while_one(self):
+ # Skip over: LOAD_CONST trueconst JUMP_IF_FALSE xx POP_TOP
+ def f():
+ while 1:
+ pass
+ return list
+ asm = disassemble(f)
+ for elem in ('LOAD_CONST', 'JUMP_IF_FALSE'):
+ self.assert_(elem not in asm)
+ for elem in ('JUMP_ABSOLUTE',):
+ self.assert_(elem in asm)
+
+ def test_pack_unpack(self):
+ for line, elem in (
+ ('a, = 1,', 'LOAD_CONST',),
+ ('a, b = 1, 2', 'ROT_TWO',),
+ ('a, b, c = 1, 2, 3', 'ROT_THREE',),
+ ):
+ asm = dis_single(line)
+ self.assert_(elem in asm)
+ self.assert_('BUILD_TUPLE' not in asm)
+ self.assert_('UNPACK_TUPLE' not in asm)
+
+ def test_elim_extra_return(self):
+ # RETURN LOAD_CONST None RETURN --> RETURN
+ def f(x):
+ return x
+ asm = disassemble(f)
+ self.assert_('LOAD_CONST' not in asm)
+ self.assert_('(None)' not in asm)
+ self.assertEqual(asm.split().count('RETURN_VALUE'), 1)
+
+
+
+def test_main(verbose=None):
+ import sys
+ from test import test_support
+ test_classes = (TestTranforms,)
+ test_support.run_unittest(*test_classes)
+
+ # verify reference counting
+ if verbose and hasattr(sys, "gettotalrefcount"):
+ import gc
+ counts = [None] * 5
+ for i in xrange(len(counts)):
+ test_support.run_unittest(*test_classes)
+ gc.collect()
+ counts[i] = sys.gettotalrefcount()
+ print counts
+
+if __name__ == "__main__":
+ test_main(verbose=True)